build: only add dependencies if needed
build: only add dependencies if needed

The dependencies may be empty which will fail.  Guard against that.

e78l/swift-corelibs-foundation,parkera/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,apple/swift-corelibs-foundation,e78l/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,parkera/swift-corelibs-foundation,e78l/swift-corelibs-foundation,apple/swift-corelibs-foundation,parkera/swift-corelibs-foundation,parkera/swift-corelibs-foundation,e78l/swift-corelibs-foundation,parkera/swift-corelibs-foundation,e78l/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,apple/swift-corelibs-foundation,JGiola/swift-corelibs-foundation